1. Field of the Invention
The present invention relates to a process of extracting vegetable oil and fat, and particularly relates to a process of extracting vegetable oil and fat by contacting a flaked oleaginous material with an ethanol solution of high ethanol concentration.
2. Description of the Prior Art
Methods of extracting vegetable oil and fat by contacting an ethanol solution with an oleaginous material are known; for example, Japanese Kokai No. 51-89506 (U.S. Pat. No. 3,970,764), Japanese Kokai No. 52-38050 (U.S. Pat. No. 4,219,470), and Japanese Kokai No. 53-77249 (U.S. Pat. No. 4,144,229). However, in these known processes, a dehydration step is required to increase oil solubility in ethanol. For the dehydration process, a distillation is typically used. However, there are many problems in distillation. For example, ethanol and water form a minimum boiling mixture theoretically at 96 weight % ethanol, but in practical processes at 94 weight % ethanol. Since the oleaginous raw material contains some water originally, the ethanol concentration of the extracted solution is from 92 to 93 weight % after the extraction process. Within this range oil solubility is from 4.9 to 6.3 weight % even at the boiling point of the ethanol solution. Therefore it is necessary to use precision distillation methods to obtain highly concentrated ethanol solution, for example, reduced pressure distillation, extractive distillation, and azeotropic distillation. But reduced pressure distillation and extractive distillation have problems associated with their operation such as loss of ethanol. Azeotropic distillation requires other chemicals, such as benzene or cyclohexane, which are undesirable for the foods industry. Furthermore, distillation methods require several times as much energy as the latent heat of ethanol. Therefore, they are unsuitable for practical plant operations.